5-HTP can cross the blood-brain barrier and increase central nervous system (CNS) synthesis of serotonin. Healthy serotonin levels are associated with deep, restful sleep. L-theanine is a naturally occurring amino acid (found in tea) and is often used to help reduce occasional stress. The release of melatonin mirrors the body’s cycle of day and night, with the highest levels of melatonin produced at night. Melatonin can help regulate the sleep cycle, and healthy melatonin levels are known to be important for restful sleep and recovery.